塔河油田西部斜坡TH10421井区中—下奥陶统迷宫型缝洞结构特征

Structural characteristics of maze-type fracture-cavity ofMiddle-Lower Ordovician in Well TH10421 Block inwestern slope of Tahe Oilfield

为了明确塔河油田上奥陶统厚覆盖区TH10421高累产井区的古岩溶洞穴成因及缝洞结构关系,利用古地貌恢复、地震属性提取、缝洞体雕刻等方法,厘清研究区地表水系分布特征、断裂特征、洞穴空间结构,首次识别出塔河油田TH10421井区的缝洞系统为洪水成因迷宫型洞穴系统,并结合油藏动态生产特征分析迷宫型洞穴系统的缝洞体连通关系。研究结果表明:TH10421井区发育共轭型次级走滑断裂网络,网格状断裂为迷宫型洞穴提供初始溶蚀通道;加里东运动中期Ⅱ幕地表岩溶湖泊提供高流量岩溶水补给,岩溶水沿网格状断裂下渗注入一间房组形成迷宫型洞穴;岩溶水顺断裂的溶蚀表现为同时性、选择性特点,造成TH10421井区迷宫型洞穴在不同方向断裂和不同深度上的溶蚀程度差异较大,东部浅层洞穴管道的连通性好,西部浅层洞穴管道的连通性较差,深层缝洞的连通性好。

In order to understand the paleo-karst cave genesis and fracture-cavity structures in Well TH10421 Block,which has high cumulative production in the thick coverage area of Upper Ordovician in Tahe Oilfield,the distribution characteristics of the surface water system,fracture characteristics,and spatial structure of caves in the area are clarified through paleo-geomorphic restoration,seismic attribute extraction,and fracture-cavity body carving.The fracture-cavity system in Well TH10421 Block is defined as a maze-type cave system caused by flood for the first time.According to the reservoir’s dynamic production characteristics,the connection relationship between fracture-cavity bodies of the maze-type cave system is analyzed.The results suggest that the conjugate secondary strike-slip fault network is developed in Well TH10421 Block,and gridded faults provide an initial dissolution channel for maze-type caves.In episodeⅡof the middle Caledonian movement,surface karst lakes provide a high-flow karst water supply,and the karst water infiltrates into Yijianfang Formation along the gridded faults to form maze-type caves.The dissolution of karst water along the faults has the characteristics of simultaneity and selectivity,which results in great differences in the dissolution degree of maze-type caves in Well TH10421 Block in terms of different fault directions and depths.The connectivity of the pipeline in the shallow cave in the east of maze-type caves is excellent,while that in the west of maze-type caves is poor,and the connectivity of the deep fracture-cavity is great.